# In-Depth Look: How to Use Common Factors to Factorise ^

## Transcript

Again guys what I’m going to do is trying to expand that out in an expansion in expanded form. So I’ve got one we’ve got two b’s because it’s b squared so I put bb and three c, so ccc, because it’s c cubed right? I just put it like that you don’t have to do this every single time you do a question.

But until we get the hang of it I’m just going to put it like this so you get the id. But in your working out like you don’t have to do that if you get confused you can but you should get used to this in a while. So guys ask yourself what is common? Here we have an a. Is there a here yes. We’ve got a here and a here we’ve got a b here we’ve also got a b here so we only take one b out okay because we’ve only got one b there.

If there was two b here we’ll take two b because this one also has two b but this one only has one so we also take just one b out from here as well. And we’ve got ac here I’ve also got three c’s but because this one only has one c I’m also going to take out one c from the other one of the terms okay? So basically I’m the common factor is abc, so let’s take abc out like that, so here we took abc all out so we just have one left it’s not zero guys it’s one some people say zero okay because when we expand guys abc times one is abc. Okay?

If I have zero I won’t get abc right? So make sure that’s one and I took one a out, I took one b out, I took one c out. so we have b and two of the c, so c times c which is c squared. So we have c squared left inside there. Factorize three a minus a squared b, so again I’m going to make that a squared a a. Just for the take of you being able to see what the common factor is.

So we have a 3 here but we don’t have any 3 here. We’ve got an a here and we’ve also got a’s here we’ve got two a, but we only take one a out because this one only has one a, so if I take a out, I’ll have three minus ab just ab because I took that a out. Okay? that’s the idea.

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